问题: Thetroposphereisthewarmestpartoftheatmospherebecauseit_______.
A: containsalayerofozonegases.
B:about42degreescolderthanontheground.
C:21%oxygenbyweight.
D:lessthan1%ofxenonbyvolume
E:about75degreescolderthaninInterlaken
F:iswarmedbytheearth’sheat.
